In the field of radiography it is common to enclose an x-ray film in a cassette, sandwiching the film between the surfaces of intensifying screens, which are mounted on foam pads affixed to the interior surfaces of top and bottom panels which form two opposing sides of the cassette. Normally, the top and bottom panels are attached along one edge of each to a hinge to allow the cassette to be opened for insertion of a fresh film, or removal of an exposed film. A latch means is usually provided on the edges opposite the hinge edge, to hold the cassette in the closed state, and both panels have borders on all four edges that cooperate to keep light from entering the closed cassette.
Often, cassettes of the above type contain means to allow patient identification data to be optically printed onto a portion of the x-ray film contained within the cassette. Typically, this comprises an aperture through one of the panels, generally located over one corner of the enclosed film. Commonly the aperture has a sliding shutter, which is closed to render the cassette light tight, and opened, to allow the patient identification information to be optically projected onto the film, through the aperture. The sliding shutter usually has locking means to hold it in the closed position, said locking means being defeated by mechanical or magnetic elements in a patient identification camera designed to work with the shutter locking means.
Patient identification windows of the above type may on occasion fail to open properly, resulting in a failure to properly transfer the patient identification to the film, or they may fail to close properly, resulting in fogging of the enclosed film.
From the foregoing discussion it should be apparent that there remains a need in the art for a patient identification system that can operate effectively without moving parts.